7
1)(1-y)(1+y)/(1-y) - 2y=1+y-2y=1-y
2)(1-y)*(y+1)/(1-y)²=(y+1)/(1-y)
3)(y+1)/(1-y)-2y/(1-y)=(y+1-2y)/(1-y)=(1-y)/(1-y)=1
8
x/y=1/2⇒y=2x
(4x²-9y²+2xy)/(3y²+16x²)=4x²-9*(2x)²+2x*2x)/(3*(2x)²+16x²)=
=(4x²-36x²+4x²)/(12x²+16x²)=-28x²/28x²=-1
9
(8x²+14x+3)/(2x-1)(4x²+2x+1) -(1-4x)/(4x²+2x+1)-3/(2x-1)=
=(8x²+14x+3-2x+1+8x²-4x-12x²-6x-3)/(2x-1)(4x²+2x+1)=
=(4x²+2x+1)/(2x-1)(4x²+2x+1)=1/(2x-1)
1/(2x-1)=1/(2x-1)